docker 数据量 vs Kubernetes 持久化存储

Question

docker engine supports data volumes

A Docker data volume persists after a container is deleted

docker run and docker-compose both support it:

1. docker run --volume data_vol:/mount/point
2. docker-compose with named volumes using top-level volumes key

kubernetes also supportspersistent volumes , but does it support the same concept of having a data volume - that is, a volume which resides within a container?

if kubernetes supports a data volume (within a container):

1. would appreciate any reference to the documentation (or an example)
2. does it also support the migration of the data volume in the same manner it supports the migration of regular containers?

i found some related questions , but couldn't get the answer i am looking for.

Answer 1

What you are trying to say is:

If you do not specify a host path for a docker volume mount, docker dynamically provisions a path and persist it between restarts.

"that is, a volume which resides within a container" Volume is generated outside of container and mounted later.

For example:

# data_vol location is decided by docker installation
docker run --volume data_vol:/mount/point

# host path is explicitly given
docker run --volume /my/host/path:/mount/point

In kubernetes terms, this is similar to dynamic provisioning. If you want dynamic provisioning, you need to have Storage classes depending on your storage backend.

Please read https://kubernetes.io/docs/concepts/storage/dynamic-provisioning/ .

If you want to specify a host path, following is an example. You can also achieve similar results by using NFS, block storage etc.

apiVersion: v1
kind: PersistentVolume
metadata:
  name: my-pv
spec:
  accessModes:
  - ReadWriteOnce
  capacity:
    storage: 10Gi
  hostPath:
    path: /home/user/my-vol
---
apiVersion: apps/v1
kind: StatefulSet
metadata:
  name: my-ss
spec:
  replicas: 1
  selector:
    matchLabels:
      app: my-ss
  serviceName: my-svc
  template:
    metadata:
      labels:
        app: my-ss
    spec:
      containers:
        - image: ubuntu
          name: my-container
          volumeMounts:
            - mountPath: /my-vol
              name: my-vol
  volumeClaimTemplates:
    - metadata:
        name: my-vol
      spec:
        accessModes:
        - ReadWriteOnce
        resources:
          requests:
            storage: 10Gi
        selector:
          matchLabels:
            app: my-ss